This invention relates to a marine acoustic survey and, more particularly to a marine acoustic array configured to alter turbulence conditions encountered by the array as it is towed along a line through a water layer so as to reduce tow noise effect on array contained hydrophones and other sensors.
In conducting a marine acoustic survey, an acoustic energy source is employed by an exploration vessel to generate an acoustic signal, referred to as a pressure wave, which is transmitted through the water layer into the subsurface formations. A portion of the signal is reflected from the subsurface reflecting interfaces back to the water layer where it is received by an acoustic array being towed behind the exploration vessel. The array is comprised of a plurality of acoustic sensors which generate electrical signals in response to the received acoustic signals. The acoustic signals are spread along the length of the array and are electrically connected through the array to recording instruments on board the exploration vessel. Such a marine acoustic survey may be typically carried out with the exploration systems of the type described in U.S. Pat. No. 4,357,698 to W. H. Ruehle and U.S. Pat. No. 4,581,724 to R. G. Zachariadis.
In such a marine acoustic survey numerous problems are encountered in the recording of marine data that are not encountered during a land survey. A primary one of these problems is water turbulence created by the movement of the array along a line through the water layer resulting in array tow noise. Reducing tow noise is of particular interest as it creates distortion in the received acoustic reflection signals.
It is, therefore, a primary object of the present invention to provide for a marine acoustic array that can alter such water turbulence during marine acoustic surveys so as to reduce array tow noise and thereby provide acoustic reflection signals with improved signal-to-noise ratios. Reducing noise will permit detection of deeper events and better resolution of events at all levels.
A further object is a reduction of tow noise in fixed and towed applications for locating and identifying marine vessels and marine life forms.